By the thoroughbred Hill Tarquin, with breeding going back to the great Man O'War, he was originally discovered in Co Clare as a three-year-old by his long-time rider and owner, American Kim Walnes. Having finished second to Carawich in 1981, he went one better 12 months later.
Winner of the gold medal in 1978 with the American thoroughbred Might Tango, Bruce Davidson went on to win at the venue a further five times over the years. One victory of note came with Happy Talk in 1993.
Sourced here through long-established event horse agent Clare Ryan, the gelding was originally destined for the show ring but proved a versatile competition horse in the eventing field. By Hard Talk, he was out of the mare Blarney Rose, by Mon Capitaine.
Mon Capitaine is best known as sire of Captain Christy, winner of the 1974 Cheltenham Gold Cup, and of the 1980 Champion Chase winner, Another Dolly.
This pedigree traces back to Wild Risk and the same family as the great stallion Bassompierre, who also sired Custom Made, the winning mount of David O'Connor in the Olympic trials in 1995.
Bred in Ireland by the late Kitty Horgan and her daughter, veterinary surgeon Liz O'Flynn, Custom Made is one of many success stories from the Rolex over the years. He also carried substantial Irish Draught blood, being out of a mare by Ben Purple.
Wilton Fair (by Wilton House) was O'Connor's mount in 1990, but the legendary rider will also be well remembered for his success with the great Irish Sport Horse Giltedge, winner of only the fourth running of the four-star event in 2001.
Like Custom Made, he was also sourced in Ireland by William Micklem, who was again attracted to his thoroughbred/Irish Draught breeding.
By Glen Bar, who was by the thoroughbred stallion Bahrain, and out of a thoroughbred mare by Awkward Brief, he carried 25pc Irish Draught blood through Glen Bar's grandam Kealkil Lass.
This breeding again came to the fore in 2008 through Philip Dutton's winning mount Connaught, and in 2014 thanks to Bay My Hero, the mount of William Fox-Pitt.
Although warmblood stallions dominate so many pedigrees worldwide today, records show that even up to 2012 50pc of individual Olympic medallists in equestrian were thoroughbreds, as were 42.5pc of horses on medal-winning teams. In fact thoroughbreds also made up more than 28pc of the start list for the Rolex in 2015, while seven of the top-10 finishers were of Irish descent.
For followers of tradition, Master Frisky is one who is expected to fly the ISH flag once more this year, having finished an impressive seventh last year under Boyd Martin.
By the thoroughbred Master Imp, he carries full Irish Draught blood through his damsire Coopers Hill.
Finishing one place ahead of this combination last year was Will Coleman on OBOS O'Reilly, a son of the Oldenburg sire OBOS Quality 004 out of the ISH mare Omard Clover Queen, by Clover Hill.
The rider is hoping to improve on that placing this time round and had a good result of fifth at the recent Carolina Horse Trials. The Thomas Hughes-bred pair of HHS Cooley and Sir Donovan will both represent the USA. They are half-brothers out of Flown, by Imperius, and from the same family as show jumpers Flo-Jo, Echo Beach and Beach Ball.
It is not often that eventers boasting Connemara breeding make the cut for the Rolex, but Sparrow's Nio is one such entry that is again expected to gather much interest.
By the deceased Connemara stallion Grange Finn Sparrow, the 15.3hh gelding is out of the unraced thoroughbred mare Ms Lady Longneck.
Bred in the west by Lady Maria Levinge, Grange Finn Sparrow was originally exported to Austria and arrived in the States in the 1980s, after which he went on to breed many other eventers including Windswept and Galway Blazer.
"I first got interested in Connemaras when I rode Briar Fox Mundugus who is also by the same sire, but he was sadly killed in 2010," commented Allie Sacksen, owner and rider of Sparrow's Nio.
"I discovered Nio that same year when he was just seven but he had done no eventing, so we basically had to start from scratch."
Now 12, the feisty grey has come a long way and in their preparations for the Rolex finished 10th in the recent CIC*** at Pine Top International Horse Trials.
"He's like a grumpy old man but he is simply amazing cross-country and although there's thoroughbred in there, he has all the trademarks of a Connemara pony.
"We finished the Rolex last year but I would hope to be better placed this time round," Ms Sacksen added.
Entries for the 2016 Rolex closed last week and among the international entries are 2015 winner Michael Jung of Germany with FischerRocana FST, and last year's runners-up Tim Price and Wesko for New Zealand.
Also a winner of Burghley last autumn, if Michael Jung can add the Rolex to his list once again he will be a strong contender for the Rolex Grand Slam of Eventing in the lead up to Badminton in early May.
Boasting a winner's purse of $350,000 (€308,000), the accolade is awarded to a rider who can win the Rolex, Badminton and Burghley in any consecutive order. British rider Pippa Funnell still holds the title of the only rider to complete the treble in 2003.